The U.S. Department of Energy’s National Nuclear Security Administration (DOE/NNSA) will conduct low-altitude helicopter flights over the route of the Boston Marathon, from Hopkinton to Boston, between April 12th and April 15th to measure naturally occurring background radiation.

The public may see a twin-engine Bell 412 helicopter, which is operated by the Remote Sensing Laboratory Aerial Measuring System from Joint Base Andrews and is equipped with radiation sensing technology.

The helicopter will fly in a grid pattern over the area at 150 feet (or higher) above the ground surface at a speed of approximately 80 miles per hour. Flyovers will occur only during daylight hours and are estimated to take about three days to complete.

The measurement of naturally occurring radiation to establish baseline levels is a normal part of security and emergency preparedness for major public events.

NNSA routinely notifies the public of upcoming flights so that citizens who see the low-flying aircraft are not alarmed.

DOE/NNSA has conducted these flights in support of the Boston Marathon since 2014.